The present invention relates to novel azeotropic compositions, a process for the production of foams in which these azeotropic compositions are used and to foams produced using these azeotropic compositions.
The use of trichloromonofluoromethane (CFC-11) and other chlorofluorocarbons as blowing agents in the production of urethane foams is well known. These CFC blowing agents are also known to have an adverse effect upon the ozone layer in the atmosphere. The urethane foam industry is therefore investigating methods for producing foams with good physical properties without using CFC blowing agents.
Initially, the most promising alternatives appeared to be hydrogen-containing chlorofluorocarbons (HCFCs). U.S. Pat. No. 4,076,644, for example, discloses the use of 1,1-dichloro-2,2,2-trifluoroethane (HCFC-123) and 1,1-dichloro-1-fluoroethane (HCFC-141b) as blowing agents for the production of polyurethane foams. However, HCFCs also have some ozone depletion potential. There is therefore mounting pressure to find substitutes for the HCFCs as well as the CFCs.
Alternative blowing agents which are currently considered promising because they contain no ozone-depleting chlorine include volatile organic compounds which contain no halogen and mixtures of such organic compounds.
JP 07,133,368, for example, discloses the use of dimethoxymethane as a blowing agent for rigid polyurethane foams.
U.S. Pat. No. 5,096,933 discloses a process for the production of rigid polyurethane foams in which cyclopentane and/or cyclohexane and optionally a low boiling compound (i.e., boiling point less than 35.degree. C.) with no more than 4 carbon atoms which is homogeneously miscible in cyclopentane and/or cyclohexane is used.
The azeotropic mixtures taught in U.S. Pat. No. 5,166,182 must have boiling points below 50.degree. C. These azeotropic mixtures are formed from organic compounds having surface active properties that enable the blended azeotropic mixture to become miscible with polymer resins. Examples of the organic compounds described as being useful in the production of such azeotropes include: n-pentane, acetone, methyl alcohol, methyl formate, ethyl formate, ethyl alcohol, 2-methyl butane, nitromethane, cyclopentane, 2,3-dimethyl butane, 2,2-dimethyl butane and dimethyl sulfide. These azeotropes may be used in combination with fluorocarbons.
Azeotropic compositions made up of dimethoxymethane and cyclopentane have not, however, been disclosed in the prior art. Nor has the usefulness of such azeotropic compositions as blowing agents for foams been disclosed in the prior art.